A virgin queen flies out to a drone congregation area (DCA) and mates in the air with a dozen or more drones drawn from the surrounding countryside. Honeybees determine sex with a single complementary sex-determiner (csd) gene: an egg that is heterozygous at this locus (two different alleles) develops into a female worker, but an egg that is homozygous (both alleles the same) develops into a sterile diploid drone — which nurse bees detect and eat as young larvae. A patchy, "shotgun" brood pattern is the classic field sign of this happening too often.
2 / Ne — so halving Ne roughly doubles the loss.Real breeding programmes fight this exact trap with drone-flooding apiaries, queen rotation across unrelated lines, instrumental insemination and genetic monitoring — all ways of pushing Ne back up so brood patterns stay solid.
A virgin queen's mating flight through a drone congregation area, and the brood-comb consequence: how few distinct sex alleles among available drones drive up diploid-drone losses and produce a patchy brood pattern.
Honeybee sex is set by a single csd gene locus. Matings that pair two identical alleles produce diploid drones, which are eaten as larvae — visualised here as dark, empty comb cells that scale directly with how few unrelated drone sources (effective population size, Ne) the queen can draw on.
Drag the diversity slider to change Ne, set how many drones the queen mates with, or pick a drone-source preset. Watch the mating-flight trail lines turn red on a doomed match, and see the brood comb fill in — or gap out — in response.
Breeders counter this exact trap with drone-flooding apiaries, queen rotation across unrelated lines, instrumental insemination and genetic monitoring — all deliberate ways of keeping Ne high enough to avoid a spotty brood pattern.